Conventional anesthesia apparatus or machines commonly incorporate two separate vaporizers. Each vaporizer is arranged to dispense a metered amount of anesthesia vapor, e.g., Halothane, Enflurane, Methoxyflurane, etc., into the patient breathing circuit, or fresh gas line.
While the construction of commercially available vaporizers varies from manufacturer to manufacturer, the most common type of vaporizer comprises a canister including a reservoir of the anesthesia, valve means and a rotatable dial coupled to the valve means for adjusting the valve means to establish the vaporizer concentration levels. For example, the VAPOR vaporizer used in anesthesia machines sold by N.A.D. Inc., the assignee of the instant invention, includes a rotary dial for adjusting the opening of a valve in the vaporizer to divide the gas flow in the vaporizer in accordance with the dial setting. Part of the gas flow passes through a by-pass, without entering the vaporizer chamber (where the anesthetic is located), while the remaining portion of the gas flow is lead through the vaporizer chamber for saturation by anesthesia vapor. The gas flow which is saturated with the vapor is then combined with the by-pass gas flow so that the whole amount of gas leaves the vaporizer at the set concentration. In the VAPOR vaporizer, the introduction of the gas with the anesthesia vapor into the fresh gas line is effected by an outlet valve under the control of a separate on/off switch. A pair of rotary cams and a pivoting lever are provided to serve as an interlock to insure that the outlet of the vaporizer is opened when the rotary dial is adjusted to any particular setting and to prevent the adjustment dial from being rotated to any setting when the on/off switch is closed, thereby precluding any gas from passing into the vaporization chamber when the outlet of the vaporizer is closed.
In a dual vaporizer anesthesia machine, it is desirable to provide means for preventing both vaporizers from being opened simultaneously since such action prevents an uptake of the vaporizing agent from one vaporizer into the other, which occurrence may have a detrimental effect on the patient. To that end, there is disclosed in U.S. Pat. No. 4,307,718 (Schreiber) a vaporizer exclusion mechanism (hereinafter known as a "vaporizer interlock") to prevent such simultaneous opening. U.S. Pat. No. 4,307,718 (Schreiber) is assigned to the same assignee as the present invention, namely N.A.D., Inc. and whose disclosure is incorporated by reference herein.
In particular, this vaporizer interlock is an interlock device that insures that one vaporizer is closed whenever the other is open and comprises a pair of reciprocable pins and a cooperating pivotable lever. Each pin is arranged to be extended into a cam recess located in a rotary dial on each of the vaporizers (the rotary dial establishes the vapor concentration to be provided) by pivoting action of the lever. Rotation of one dial automatically causes the pin located therein to move out of the cam recess and into contact with the lever. This action pivots the lever and causes it to contact the other pin to extend the other pin into the recess in the associated vaporizer dial, thereby locking the dial closed.
It is therefore desirable to connect any type of vaporizer to the vaporizer interlock disclosed in U.S. Pat. No. 4,307,718 (Schreiber) regardless of the vaporizer configuration.
As shown in FIGS. 1A-1B, there is shown a vaporizer interface 20 that permits the connection of an Ohmeda TEC 6 vaporizer 22 to the vaporizer interlock. As can be seen most clearly in FIGS. 1A and 1B, the TEC 6 vaporizer 22 is directly coupled to the vaporizer interlock L-shaped mounting bracket 46. However, the TEC 6 vaporizer comprises a control knob 24 that does not directly interact with interlock reciprocable pin 54 as disclosed in U.S. Pat. No. 4,307,718 (Schreiber); instead, a series of linkages 26A, 26B and 26C are utilized to couple reciprocable pin 54 movement with the control knob 24 movement. Other than that distinction, operation of the vaporizer interlock with the TEC 6 vaporizer 22 is in accordance with U.S. Pat. No. 4,307,718 (Schreiber): With regard to a common vaporizer interlock and depending on the status of the other vaporizer(s), not shown, the reciprocable pin 54 is either in an extended state (FIG. 1A) or in a retracted state (FIG. 1B). If the reciprocable pin 54 is in the extended state, the internal linkages 26A, 26B and 26C are driven to pivot such that the control knob 24 is "locked-out", thereby preventing the operator from opening the TEC 6 vaporizer 22. (FIG. 1A). On the other hand, if the other vaporizer(s) are in the "locked out" state, the operator can rotate the control knob 24 causing the internal linkages 26A, 26B and 26C to pivot such that the reciprocable pin 54 is retracted, thereby permitting the metered flow of gas from the TEC 6 vaporizer 22.
However, use of the Ohmeda TEC 6 vaporizer 22/interlock interface 20 is restricted to those vaporizers having the same internal construction. For example, the vaporizer interface 20 cannot operate with a DATUM.TM. vaporizer manufactured by Blease (located in the United Kingdom) which utilizes a vertically-oriented control knob that must be pushed-in before it can be rotated. Therefore, there remains a need for a vaporizer interface that can couple any vaporizer to the vaporizer interlock disclosed in U.S. Pat. No. 4,307,718 (Schreiber).